Contact for electromagnetic mechanism.



R. A. PBSSENDEN. CONTACT FOR ELECTROMAGNETIC MECHANISM. APPLICATION rum)MAILIB, 1906.

7 Patented De0.31, 1912.

WITNESSES: i

(H 9.4 L3 WW wwzmmm UNITED STATES PATENT OFFICE.

REGINALD A. FESSENDEN, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR,IBY MESNE ASSIGNMENTS, TO SAMUEL M. KINTNER, OF PITTSBURGH,PENNSYLVANIA, AND HALSEY M. BARRETT, OF BLOOMFIELD, NEW JERSEY,RECEIVERS.

Specification of Letters Patent.

Application filed March 16, 1906. Serial No. 306,387.

To all whom it may concern:

Be it known that I, REGINALD A. FEssEN- DEN, a citizen of the UnitedStates, and resident of Washington, District of Columbia, have inventedcertain new and useful Improvements in Contacts for ElectromagnetlcMechanism, of WhlCh the following is a specification.

The invention relates to electrical contacts, and is especially adaptedfor use'in sensitive relays.

Great difficulty has been experienced in the use of relays from thesparking and consequent weldln together of the contacts, even when a conenser is used across the contacts. And further the surfaces of thecontacts become oxidized or otherwise deteriorated so that the pressureof one contact on the other is not suflicient to break or destroy theresisting film and permit of the completion of the circuit.

My invention has for its object the prevention of a weld betweencontacts and the rupture of such weld, if formed, without interferencewith the operation of the relay or other instrument.

It is a further object of the invention to prevent the formation of anon-conducting film on the surfaces of the contacts and its removal orbreaking up if formed, as hereinafter more fully described and claimed.

In the accompanying drawing forming a part of this specification isshown diagrammatically a relay a bell.

In the practice of my invention a finger 1 is attached to the movablepart or member of a relay, as for exam Ie the movable coil 2 of theWeston type 0 relays. This finger is preferably made so that it willbend or flex under slight pressure, and has suflicientresilience toreturn to normal position when relieved of the pressure. This finger ispro- .vided on one or both sides, dependent on the use to which therelay is put, with contacts 3., Similar contact or contacts, 4, aresecuredto springs or yielding members, 5 and 6, adapted to yield-read1ly under sli ht pressure and return to normal osition w en thepressure is relieved. ile I have shown my improvement as applied to theand circuits for operating operation of a bell, only one stationary con-The springsor yielding members, 5 and 6, are secured to suitablesupports, 7 and 8, and means such as screws 9 are provided for adjustingsuch members. The springs 5 and 6 are connected to one pole of abattery, 10, which has its opposite pole connected to the finger, 1,.and a bell or other device, 11, is included in this circuit. Acondenser, 12, or resistance, 13, or both, may be connected in shuntacross the fixed and movable contacts.

It has been found experimentally that the sparking and welding 15 due tothe chattering which occurs when the movable contact touches the fixedcontact. If however the parts carrying the fixed contact or contacts, orthe finger carrying the movable when one contact touches the other willbe avoided. Any elasticity or flexibility will not attain the desiredobject,- but the proper elasticity must be attained empirically, whenthe vibrations will be damped and thus sparking avoided. It will also benoted that by means of the screw 9 the tension of the arm 5 may bevaried and this will vary the period of vibration, so that the swing ofthe arms 5 and 1 may be made to coincide, which will eflect a furtherdecrease in chattering,

In case sparking and welding should oc cur, provision is made by makmgthe contacts in the form of segments of spheres, for

the rupture of such weld. Since the centers,

of motion of the arms are widely separated, the contacts in swingingwill rub or roll one on the, other, thereby exerting such a leverage aswill easily break any weld which may be formed.

It has been determined in a series of experiments with'electricalcontacts, that almost all metal contacts deteriorate in time when thepressure of one contact on the other is very'slight. For example theresistance of silver or platinum contacts will run up to thousands ofohms in a few days or hours. I have ascertained that contacts made ofany alloy of platinum and iridium, preferably an alloy containing 5% or10% of ididium will not deteriorate, and the resistance will not risematerially if at all even when the contacts are pressed together verylight, the pressure being of the order Patented Dec. 31, 1912.

of one tenth of a milligram. This discovery I of the benefit derived bythe use of this alloy bears no relationto my previous discovery thatthe, high tem erature due to arcing in induction coils, di notdeteriorate contacts formed of platinum iridium. In the present case thegood results are due to the fact that thin high resisting coatings orfilmswill not form on platinum iridium contacts, even when there is notany heating .from sparking. The arrangement of the spherical contacts onthe yielding supports is further advantageous as when the movablecontact bears against the other contact, both will move slightly in thesame direction and there will be a rolling and a rubbing movement of onecontact on the other tending to remove or break down any resisting film.

I claim herein as my invention:

'1. An electrical contact device comprising aplurality of contactmembers mounted respectively on resilient and upon resilient and pivotedsupports, said members being of rounded form, whereby in making contactthe members both'slide and rotate in contact with each other,substantially as described.

2. An electrical contact device comprising electrodes made of platinumiridium of general spherical form and mountings for said electrodes inthe form of pivoted and resilient arms, whereby to prevent sparking.

In testimony whereof, I have hereunto set my hand and seal, the 12th dayof March A. D. 1906.

REGINALD A. ZFESSENDEN. [1.. 'S.]'

Witnesses:

JESSIE E. BENT, PHILIP P051.

